This invention relates to a charge control agent for electro photography including a monoazo metals-compound and a toner for developing an electrostatic image including the agent.
An electro photography system performs to develop an electrostatic latent image by toner which are carried out frictional electrification, transferring and fixing toner image onto paper, to obtain images and characters.
In order for obtaining high resolution images, fine pulverized toner or resins having a high acid value therefor are used. If the pulverized toner had insufficient electrostatic charge, the toner image cannot be developed vividly and may cause foggy. For giving a sufficient frictional electrification property, a charge control agent is pre-added to the toner. It is known as the charge control agent having a negative electrification property, metallic complex salts of monoazo dyes, metallic complex salts of salicylic acid or naphthoic acid or dicarboxylic acid, copper phthalocyanine pigments and resins including acids-component. It is known as the charge control agent having a positive electrification property, nigrosine dyes, azine type dyes, triphenylmethane type dyes, resins of quaternary ammonium salt and resins having quaternary ammonium groups at a side chain thereof.
For instance, the metallic complex salts of monoazo dyes are mentioned in Japanese Patent Provisional Publication Nos. 63-267793, 7-97530, 9-169919, 10-186713, 11-7164 and 2001-26337.
However, the conventional charge control agents may decompose and deteriorate to lose a charge control property and make poor stability when being exposed to mechanical friction, mechanical shock, electric shock, optical irradiation, temperature change, high temperature, humidity change or high humidity. Moreover, when the toner image is transferred and fixed onto the paper with heat or pressure, the resins having a high acid value in the toner may make the charge control agent decompose or sublimate to cause the image on the paper to be indistinct. Furthermore, the rise speed of the electrification is so slow that the electrostatic charge becomes insufficient in an early stage of the development, thus the toner image is not developed vividly and will deteriorate on the way of the development.
The present invention has been developed to solve the foregoing problems.
It is an object of the present invention to provide charge control agent for electro photography including monoazo metals-compound which causes the sufficient frictional electrification property for the toner, excellent thermal resistance, excellent moisture resistance, stability and hardy sublimation. It is another object of the present invention to provide the toner including this compound for the electrostatic image development which causes resistance of mechanical friction, mechanical shock, electric shock and optical irradiation, promotion of fast rise speed of the electrification and of good quality of the developed toner image.